1. Field of the Invention
The present invention relates to an image pick-up method and an image pick-up system of a mobile-type camera system used for location of movies and television programs, and more specifically to an image pick-up method and an image pick-up system of a mobile-type camera system suitable for shooting in virtual studios.
2. Description of the Related Art
When shooting in a studio, a mobile-type camera system is used and it has a structure in which a pan head is set on a mobile base called pedestal, and a camera is placed on the pan head. Then, a cameraman shoots a scene while moving the pedestal so as to change the camera angle appropriately.
In a virtual studio, for example, there is a case where a real object image taken with the camera system in the studio and computer graphics (CG) created as its background or effect, are operated together in relation with each other while maintaining the three-dimensional relationship in position as viewed from the camera position. In such a case, techniques of analyzing the two-dimensional position of the pedestal in the virtual space, as well as the position and angle of the camera set on the pedestal, are employed. That is, according to these techniques, when the two-dimensional position of the pedestal and the position and angle of the camera are determined, the relationship among the positions of the pedestal, camera, an object and CG can be found out by calculation. In this manner, the object taken by the camera and the CG image can be combined and moved together in relation with each other while maintaining the three-dimensional relationship between the positions of the object and the CG image.
The following are some of the examples of the conventional techniques proposed in consideration of the above.
(1) The method of recognizing the two-dimensional position of a pedestal, wherein a great number of position marks are made on the ceiling of the studio, and as the sensor provided on the pedestal reads some of the marks, the read marks are image-processed, thereby to recognize the position of the pedestal.
(2) The method of detecting the position of a pedestal, wherein a marker is set on the pedestal and the marker is read by a plurality of detection cameras provided in the studio, thereby to detect the position of the pedestal.
(3) The method of recognizing the pedestal, wherein a mark such as a bar code, which is included in the blue-back image taken with the studio camera as the background, is read by a detector, and the view corresponding the mark is image-processed, thereby to recognize the position of the pedestal.
(4) The method of detecting the position of a pedestal, wherein rails are laid in the studio and the pedestal are run on them while detecting the distance of the movement.
However, the above-described methods entail the following drawbacks, respectively.
First, as to the method (b 1), in some cases, position marks cannot be read from the position of the pedestal. More specifically, there are, usually, a great number of lighting tools which are suspended from the ceiling of a studio, and some of them physically block the view. Further, the reading of a position mark may be disturbed by illumination light.
As to the method (2), as the detectable area is widened, a greater number of detection cameras are required, thus increasing the cost.
As to the method (3), a mark included in the background image must be always located within the view of the camera, and therefore the movable range of the camera is limited. Further, when the size of the object increases in the image, such as in zoom-in for close-ups, etc., the ratio of the mark included in the background image may be excessively decreased as compared to the whole scene, thus making it impossible to detect it in the image.
As to the method (4), the movement of the camera is limited by the tracks of the rails, and therefore the applicability is low.
With any of the above-described methods, it is difficult to detect the positional relationship between the camera and the object to be shot at a high accuracy.